“Big Airplane” Safety: A Cessna 340/340A buyer’s guide

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For many reasons, the Cessna 340/340A has evolved into the world's best-selling piston-powered, cabin-class pressurized twin.

March 2015-

The typical buyer of a Cessna 340 is moving up from a high performance single engine airplane. Other buyers may be businesses already operating a turboprop or jet that are interested in purchasing a 340A for short trips with only a passenger or two on board. If you are considering the purchase of a 340, the following information should help educate you.

The Cessna 340/340A sits tall, and that alone gives many nervous passengers a feeling of "big airplane" safety. When you're used to making a step up on to the wing and then a dive into passenger and front seats, the airstair door on a cabin-class 340 can feel like quite a luxury.
The cabin configuration of 340s today is rarely other than what was at its introduction just an option: two cockpit and four cabin club seats. However, most owners remove seat number five, the forward-facing left-side seat. This results in a roomier cabin and makes getting in and out of the airplane (and egress to the cockpit) much easier. It is not difficult to install the sixth seat if all six seats are needed.
For families with small children, the removal of seat number five allows for a caretaker to sit in seat number six, the forward-facing right cabin seat, with their eyes on a toddler or two that are strapped into car seats and belted onto seats number three and four, the two aft-facing cabin seats.
RAM Aircraft offers a STC'd seventh seatbelt installation on the baggage shelf. It allows a child to sit on the shelf, or a cushion, with a legal seat belt. Owners needing an onboard potty can purchase a portable camping-­­style toilet that can be positioned on the aft baggage shelf.

Baggage is stored in the nose bay with a door on each side of the nose area. Additional baggage can be carried in the wing lockers. The size and capacity of the wing lockers depends on whether the aircraft is equipped with optional nacelle fuel tanks.
In reality, most 340s only have one wing locker cargo area. The second is what I call the "dirty wing locker," and it's used to carry oil, tools, fuel drains, etc. A kitty litter pan inside the dirty locker works great for holding all the stuff. I suggest you place every quart of oil in a one-gallon freezer bag—a leaking oil bottle is a true mess.
The aft cabin is pressurized. Therefore, the items you do not want exposed to altitude and cold temperatures should be carried in the cabin, along with any items that your passengers will need to access during flight. Food, toys, games and cosmetics are examples.

Engines and conversions
The 340 was manufactured from 1972 through 1975. The 340A was introduced in model year 1976. The original 340 had Continental TSIO-520-K engines delivering 285 hp. It was underpowered.
Soon, the mod shops STC'd 310 hp engines for these original 340s, and in 1976, the 340A was introduced with 310 hp TSIO-520-N engines. Few 1,400-hour TBO TSIO-520-N engines remain in the fleet. Most 340/340As are powered by TSIO-520-NB engines with a 1,600-hour TBO.
I would stress that engine TBO is only a suggestion for FAA Part 91 operations. In the United States there is absolutely no requirement to do an engine overhaul or exchange when reaching TBO.

Pressurization, propellers
and service documents
Early 340s had a 3.8 psi pressurization differential, and the 340A has a 4.2 psi differential. The difference in cabin altitude at the typical operating altitudes of 18,000 to 21,000 feet is small.
The propellers can be either a three-bladed heated Hartzell or McCauley. (A few 340s have MT-Propeller's four-bladed composite propellers.) Propeller TBOs may be five years and 1,500 hours, or six years and 2,000 hours.
If you are looking closely at a particular 340/340A, it is important for the propeller hours to have the correct suffix in the maintenance logs: be sure the data shows either "Since New" or "Since Prop Overhaul." A propeller overhaul will typically cost $4,000 each.
Like engine and propeller TBOs, Service Bulletins—including those titled Mandatory Service Bulletins—are 100 percent optional in piston powered aircraft operating under Part 91. A Service Bulletin may be wise to comply with, but it is optional.
The same is true for Supplemental Inspection Documents (SIDs). SIDs are Cessna's means to address aging aircraft. Once again, SIDs are completely optional in piston Part 91 operations. In many other countries, all Service Bulletins and SIDs are required. Complying with all SIDs can amount to a huge maintenance bill.
Fuel tanks
The complexity of the fuel system on a 340 receives too much publicity, in my opinion. Ask a properly trained 340 pilot about fuel management and the answer is very likely to be "it's no big deal." The technique can be learned quickly, provided you have the right instruction.
I've said for years, "Give me one three-hour cross-country with a new 340 pilot, and when we land, the pilot will be able to teach the system." The three fuel amounts to remember are 163, 183 or 203 useable gallons.
A few odd amounts may be seen with aircraft that have additional aftermarket fuel cells installed. These O&N (aka Tom's Tanks), carry 18.5 gallons each. A 340 may accommodate from one to four of these 18.5-gallon wing locker tanks; the number will depend on if optional factory nacelle fuel tanks or factory air-conditioning was installed.

Known icing conditions
Recently the FAA required certain twin Cessnas to have a cockpit placard if the aircraft was not certified for flight into known icing conditions. (This document, AD 2014-03-03, is available at CessnaFlyer.org. —Ed.) The known ice kit was only a factory option for 340s and was first available on the 340A in 1977.
The 340A known icing package consists of a fully booted airframe—this includes the wings and the wing stub between the fuselage and nacelle. The vertical and horizontal stabilizer are also booted. The propellers are heated, fuselage ice protection plates are installed, and there is heated plate on the pilot's windshield. Other items include 100 amp alternators, heated pitot tubes, a heated stall vane and heated static ports. An ice detection light illuminating the left wing boot is a part of the kit, too.
Many 340s have what is commonly referred to as full de-ice. This is not the same as the known ice kit. The term "full de-ice" generally means de-ice boots on the outer wings (but usually not on the wing stubs). The entire tail area is booted, the propellers are heated, the aircraft has fuselage ice protection plates, 100-amp alternators and heated pitot/static/stall. However, the pilot and copilot's windshield have an isopropyl alcohol anti-ice system, not a hot plate.

The four most common questions regarding maintenance are about the exhaust system AD, the landing gear, the wing spar Service Bulletin and cabin pressurization.

Exhaust system
In 1975 Cessna issued an AD addressing exhaust system maintenance. Regrettably, the AD was not properly adhered to, and in January 2000, AD 2000-01-16 was issued. In 2015, this exhaust AD is a truly accepted maintenance action.
For most pilots, the only item of adherence is a visual inspection of the exhaust system every 50 hours. By simply doing this inspection every other oil change, compliance is made easy.
At the time an engine is being overhauled or exchanged, the exhaust components must be sent to a shop certified for exhaust system inspections and repairs. Even if the components pass an inspection, few owners elect to reinstall the old exhaust components on their new engine. New exhaust components are almost always installed.
Many owners and mechanics do not fully understand the AD's requirement for exhaust removal and replacement at 12 years of age. The FAA is trying to clarify this point of the AD. The shops that are truly twin Cessna maintenance specialists usually know the rules—but shops that see only a few twin Cessnas may present an incorrect assessment
of the exhaust system to an owner or
prospective buyer.

Landing gear
The landing gear should be rigged annually. Many shops avoid this because it is a challenging task. It requires time and skill; just checking the gear tensions and lubricating the gear is not adequate. Honoring gear extension and operating speeds—VLE and VLO—is critical.
Also, high-speed turning and hard turning while braking must be avoided. It is abuse that will take its toll over time. Many twin Cessna pilots who trained with me say they can still hear my voice on rollout: "Brake straight-brake straight, no hard/fast turns."

Wing spar Service Bulletin
The wing spar Service Bulletin is not due until 15,000 hours. Most 340/340As have 5,000 to 6,000 hours. And, bear in mind, this usually took 35 to 40 years to accumulate. Therefore, 15,000 hours is a lifetime away for most pilots. (Sorry, all you Cessna Flyer readers, I will not likely be around to discuss your 15,000-hour 340 in 2050!)
Pressurization is much like a convertible automobile. It costs more to purchase, but in day-to-day use does not cost more to operate. Pressurization results in fewer headaches, less fatigue and the obvious elimination of oxygen masks. (Try putting a headset and oxygen mask on a four-year-old, or a dog.)
Twin Cessna maintenance specialists know how to find the capsule leaks that will occur. Certain shops will have a pressurization cart that allows for an aircraft to be pressurized in the hangar; a real plus in finding even small leaks.
All too often, an owner will accept a lower psi differential, resulting in a higher cabin altitude. Insist that your aircraft and mechanic get you the maximum psi for your 340 or 340A.

Depending on a pilot's experience, the training/checkout requirement will vary, but as a general rule, a first-time twin/first-time pressurized twin buyer will be required to log 25 hours of dual instruction in the aircraft, plus attend an approved school such as a Simcom training center.
At Simcom, for example, a new 340 pilot attends a five-day course with ground school on the systems and then 10 hours of full-motion simulator training. There the pilot can work through lots of malfunctions, practice lots of approaches, and make lots of mistakes; none are fatal. (Aerial Sim Training in California, a CFA supporter, is also an insurance approved training facility. —Ed.)
The dual instruction in the aircraft must be with an insurance-approved, qualified instructor. This can get some new owners in trouble. Often a new owner will have a friend or a former instructor that desires to provide the dual instruction. These pilots may be young or they may be old; they may be good pilots and good instructors—but they are not necessarily good twin Cessna/340 instructors.
An insurance requirement is that the instructor must attend school annually. (Going to King Air school or flying a 737 does not count.) Know what the term "insurance approved instructor and school" means.

If I could only give one suggestion...
I advise you to avoid maintenance based upon convenience. "Convenience can be costly" is a phrase that often applies to twin Cessna maintenance. To properly maintain a twin Cessna requires service at a shop that has experience with twin Cessnas. It is usually at a pre-purchase inspection that the consequences of maintenance by a convenient—but perhaps less-than-qualified—shop become apparent.

Let's go flying!
We will climb at a comfortable deck angle of 120 kias and will be at Flight Level 200 in approximately 25 minutes. There we will level off and set up cruise at 65 percent, which is 30 inches of MP and 2,300 rpm.
Fuel flows will be 17 to 18 gph per side and our true airspeed will be 190 to 210 knots. The cabin will be at about 7,500 feet—quite comfortable.
Taxiing out and at lower altitude we will use fresh ventilation air. If we are still warm, we will use the air conditioning. At altitude, it will be cold, yet the "free heat" from the pressurization system will likely keep us warm. If it's not enough, the 35,000 BTU heater will do the job.
We will take off and land on the mains (tiptanks). After an hour, if we have fuel in the nacelle tanks, we will transfer that fuel to the mains. We will then use up the fuel in the auxiliary tanks that are within the wings. We will then return to the mains—and land with maximum fuel in the main tanks and with the required reserve.
If the time is right for you to make your transition to a 340, the details and tips in this article should give you a nice head start as you begin your research.

Jerry Temple founded Jerry Temple Aviation (JTA) in 1995. JTA provides pilots with hands-on service from the research stage to delivery and checkout. Before founding JTA, Temple worked for 20 years in several positions in the Cessna Aircraft system, including at the Cessna factory as well as in distributor and retail sales. Send questions or comments to .

Jerry Temple Aviation
"The World's Leading Twin
Cessna Sales Specialist"